Now you can easily monitor and log air/fuel ratio on your Aeroforce gauge or other data logging device with our affordable wideband air/fuel kit. Accurate to 0.1 A/F point allowing you to accurately monitor your engine tune or PCM calibration. According to Bosch, due to the improved sensing element design the LSU4.9 shows higher lifetime robustness over the LSU4.2 This means it generally will have a longer life span and deliver more accurate readings. This sensor draws less power and has some advantages in high flow situations. It can be used in diesel applications as well, the 4.2 is not designed for this.